The Taste of our Fears

Bonnie didn't tell her friends in Mystic Falls that she was actually in New Orleans helping Klaus defeat Marcel.
More importantly, she didn't tell them that she might be developing feelings for a certain young original vampire who was also in New Orleans with his brothers.

Klaus chooses to illicit the help of many witches, one of which was Kai Parker now leader of the gemini coven after merging with Luke and succeeding.